This invention relates to a circuit interrupter having an arc runner and, more particularly to a structure for mounting an arc runner on a stationary contact.
FIG. 1 is a partial sectional side view of one example of the conventional circuit interrupter to which the present invention pertains. In FIG. 1, the circuit interrupter comprises an electrically insulating housing 1, which contains therein a movable contact assembly 2, a stationary contact assembly 3, an arc extinguisher 4 and a perforated insulating partition wall 7.
The movable contact assembly 2 has a movable contact element 201 supported by a movable contact arm 202 which is connected to an operating mechanism (not shown) as is well known in the art. The stationary contact assembly 3 comprises a stationary contact element 301, a stationary contact carrying conductor 302 carrying the stationary contact element 301, an arc runner 5 secured to the conductor 302 by a rivet 6, and a terminal portion 303 for external connection. The arc extinguisher 4 composed of a plurality of arc extinguishing plates 401 is disposed within an arc extinguishing chamber 402 defined in the vicinity of the arcing region in which an electric arc is generated between the separated contacts 201 and 301. The insulating partition wall 7 having a plurality of perforations 701 is disposed between the arc extinguishing chamber 402 and the terminal portion 303 of the stationary contact assembly 3 for preventing the ingress of any foreign matter into the interior of the circuit interrupter and for preventing the arced gas from scattering at random and melting the surrounding elements.
With the conventional circuit interrupter as above described, the arc runner 5 is mounted on the conductor 302 by a single rivet 6. Therefore, the arc runner 5 often rotates about the rivet 6 due to mechanical shocks received during current interruption and unbalanced electromagnetic force acting on the arc runner 5. When this rotation of the arc runner 5 occurs, the electric arc generated between the separated contacts 201 and 301 cannot be drawn to a proper position within the arc extinguishing chamber 4, resulting in a failure in interruption. Also, the electrical connection between the arc runner 5 and the stationary conductor 302 becomes loose and less efficient and provides a relatively large electrical resistance between them. If the arc runner 5 is to be secured to the stationary conductor 302 by means of two rivets, a step of forming an additional rivet hole in the stationary conductor 302 as well as a step of swaging the additional rivet are required, to increase the number of assembly steps and the parts of the contact arm assembly 3.